Fiber choppers are employed in conjunction with liquid resin spray dispensers to form a stream of resin-impregnated chopped fibers that are laid down on a substrate to form a glass fiber reinforced structure. Typically, a fiber chopper has a body or housing, a backing roller and a chopping roller. As an elongated glass fiber strand passes between the rollers, it is chopped into relatively short fiber segments and propelled by the action of the rollers out through a nozzle opening in the body of the chopper. The body and thus the nozzle are oriented so as to direct the stream of fibers into intersecting relationship with a stream of catalyzed resin, thus forming a stream of resin-impregnated chopped fibers. The stream of resin impregnated fibers is directed toward a substrate, and is allowed to impinge the substrate and form a layer of resin-impregnated fibers on the substrate. One such apparatus is disclosed in U.S. Pat. No. 4,071,389 to Frank E. Ives, the disclosure of which is hereby expressly incorporated herein by reference.
Although fiber choppers similar to those described in the foregoing paragraph have operated successfully to build a wide variety of glass fiber reinforced structures, two problems have been associated with their use. First, the fibers propelled from the fiber strand chopper toward the resin spray have tended to float on and around the resin spray rather than impinging the resin spray and becoming impregnated. Those chopped fibers that do not intersect the resin spray are subjected to the drag of the ambient air and are slowed down sufficiently so that they ordinarily do not reach the substrate being coated. Other chopped fiber strands are caught in the moving airstream accompanying the fiber spray and are caused to loop around the fiber spray and be misdirected either toward the floor on which the substrate rests or toward a location on the substrate that is not coated with liquid resin. As a consequence, chopped fibers are wasted during application of a resin-impregnated fiber layer on the substrate.
The second problem associated with the operation of the prior art fiber choppers and resin spray equipment is the formation of a nonuniform layer of resin-impregnated fibers on the substrate. Prior equipment produces a layer that has an arcuate upper surface that extends outwardly from the substrat. It is most desirable to produce resin-impregnated fiber layers that have a relatively uniform thickness throughout the width of the layer rather than the thicker, narrow band of material that is formed by prior art equipment.
Accordingly, it is a broad object of the present invention to provide an improved fiber chopper that when associated with resin spray apparatus will form a resin-impregnated fiber layer on a substrate, which layer has a relatively uniform thickness throughout its width. It is another broad object of the present invention to provide an improved fiber chopper that does not allow chopped fiber segments to escape impregnation by an associated resin spray and that enables utilization of substantially all of the chopper fiber segments ejected from the fiber chopper.